Plastic shell barriers are used in situations whereby a temporary safety measure is required. Plastic shell barriers are convenient in that when they are empty they are easy to transport and position as required due to their relatively light weight. Once in position plastic barriers are typically interconnected together to form a temporary barrier wall and filled with water so as to provide the barrier wall with sufficient inertia to resist and absorb impact energy during a collision. During a collision it is the purpose of the barrier wall to re-direct an impacting vehicle back onto a roadway.
One problem that exists with walls formed by a plurality of plastic barriers is that when any one barrier is impacted by a vehicle, that barrier may be pushed out of alignment with an adjacent barrier. This misalignment results in a kink or step being formed in the wall of barriers. This step or kink in the wall may result in the impacting vehicle becoming hooked by the kink or step and being spun or flipped. Ideally a temporary barrier wall should maintain alignment between adjacent barrier sections so that an impacting vehicle is re-directed away from the barrier wall at an angle of incidence substantially equal to or less than the impact angle.
Attempts to maintain alignment between adjacent barriers have been made by connecting adjacent barriers at their ends. Due to the nature of the material used to construct temporary shell barriers this requires additional reinforcing at the point of connection so as to maintain the integrity of the connection in the event of an impact. Further to the integrity of the connections, plastic shell barriers can exhibit deformation in the form of stretching, whereby the body of the impacted barrier and potentially both the impacted barrier and adjacent barrier connection there between stretch and deform. This deformation is due to the inability of the plastic material of the connections and body of the barrier to withstand the force required to move the mass of an adjacent barrier; which will typically be filled with water. The mass of a water filled barrier could be as much as 400-1000 Kg. Deformation of the connections or body of a barrier again leads to the kinking/stepping problem noted earlier.
Prior art barriers such as that recited in U.S. Pat. No. 5,425,594 teach the addition of wire cable and internal metal frameworks to provide additional resiliency to the longitudinal axis of the barrier. However such systems are complicated to manufacture and the wire cable requires tensioning in order to provide adequate tensile strength. Without sufficient tensile strength the barriers are still capable of being deformed and causing kinking or steps in a barrier wall and therefore the risk of an impacting vehicle being spun or flipped.
It will be apparent to a person skilled in the art, that an orthogonally directed impact with a single temporary plastic barrier will, depending on the inertia of the barrier and mass of the impacting object, result in that barrier being shunted in the direction of the impact. This shunting could potentially cause damage to anything on the non-impact side of the barrier, a small child for example. However, if the temporary plastic barrier forms part of an interconnected chain of temporary plastic barriers, the inertia of the impacted barrier is greatly increased. The reason for this is that an orthogonal impact force is translated via the connection portions into a longitudinal force along the line of interconnected barriers. This places a large amount of force on the connection portions as well as the body portion of the barrier sections; particularly those at or near any point of impact.
It would therefore be useful for there to be provided an easily manufacturable plastic shell barrier which is capable of being connected to adjacent plastic shell barriers and which exhibits a high resistance to tensional forces such that kinking is minimised.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.